Resistance patterns and trends of extensively drug-resistant tuberculosis: 5-year experience

Objective: Extensively drug-resistant tuberculosis (XDR-TB) strains were emerged when multidrug-resistant TB (MDRTB) was inadequately treated. Inadequate treatment of MDR-TB cases may result in additional resistance especially non-XDR-TB and then XDR-TB. The aim of this study was to know the prevalence, resistance patterns and trends of the XDR-TB strains among the MDR-TB at a tertiary care hospital in Lucknow, India Methods: A total of 430 Mycobacterium isolates were underwent NAP test and TB MPT64 Ag test for the identification of Mycobacterium tuberculosis complex (MTBC). Drug-susceptibility test (DST) was performed over MTBC for the first line drugs by 1% proportion method (Bactec) and for the second-line drugs by 1% proportion method (LowensteinJensen media). The XDR-TB status was further confirmed by line probe assay (GenoType® MTBDRsl assay). Results: Among the 430 isolates of mycobacterium, 365 (84.9%) were MTBC and 139 (38.1%) were MDR-TB respectively. Further 97 MDR-TB from “highly suspected drug resistant-TB (DR-TB)” cases among MDR-TB were tested with second line drugs in which 15 (15.5%) XDR-TB and 82 (84.5%) were non-XDR-TB. Regarding XDR-TB status, using the 1% proportion method a 100% agreement was seen with the GenoType® MTBDRsl assay. Resistance patterns of XDR-TB were as; 10/15 (66.7%) as isoniazid + rifampicin + ciprofloxacin + amikacin resistance and 5/15 (33.3%) as isoniazid + rifampicin + ciprofloxacin + amikacin + kanamycin resistance. Conclusion: The prevalence of XDR-TB was 15.5% among MDR-TB. Hence laboratory testing of “highly suspected drug resistant-TB” isolates should be done for both first and second line drugs simultaneously especially in developing countries. J Microbiol Infect Dis 2013;3(4): 169-175